for (int c0 = 0; c0 <= M; c0 += 1)
  for (int c1 = 1; c1 <= M; c1 += 1)
    S1(c0, c1);
for (int c0 = 0; c0 <= M; c0 += 1)
  for (int c1 = 1; c1 <= M; c1 += 1)
    S2(c1, c0);
